Your grandfather knew this…
That’s fish man. Hardly the same. Now a counter argument would be that eventually both the promiscuous and monogamous fish will inevitably die, one may live longer but even that one will die. But the promiscuous fish will likely produce much more offspring and more genetic diversity would be added to his line thus raising substantially the odds of his genes lasting long beyond his own life.
That may be true, but what will your offspring think of you for having brought them into this life in such a manner? 
Well the point I was actually making is that using a species lower on the evolutionary scale than even birds is hardly a valid comparison for human behavior. For a branch of the animal kingdom that’s not capable of the level of conscious thought that the family dog is capable of, quantity and diversity of future generations trumps it’s own lifespan.
Following the logic of promiscuity being bad for your health, so is self sacrifice for your own offspring. Would you support a post saying that putting your own childs needs ahead of your own is an example of bad behavior? Of course not.
The essential reason the fish is promiscuous even to the detriment of it’s own health is that in nature you WILL die…no matter how much you invest in yourself and your own survival you will die. So you put your energy into ensuring the survival of your genes. For an egg laying fish, it’s a raw numbers game. Which is easy since lacking our large brains simple animals are usually able to fend for themselves fairly quickly. But for humans it’s more about investment in fewer offspring, but make no mistake. The emotional and financial burdens that a man takes on when he chooses to raise even one child is comparable to the level of stress the fish puts into getting his genes out there as much as possible. Is it worth it? Personally from a logical perspective I think so.
Comparing what a fish does in its life to…? I believe it isn’t constructive in relating fish with a live human being that has self-awareness, or reflective thought: which is the main attribute distinguishing humans from animals or fish for that matter. It is the consciousness that enables us to think inwardly and to contemplate ourselves. It is indeed a great blessing to be aware of oneself. This is the characteristically human quality.
I can really see some key points but that thing with fish then relating it to humans is not sound doctrine.